Nonalcoholic fatty liver disease progression in rats is accelerated by splenic regulation of liver PTEN/AKT

Abstract

Background/aim: The spleen has been reported to participate in the development of nonalcoholic fatty liver disease (NAFLD), but the mechanism has not been fully characterized. This study aims to elucidate how the spleen affects the development of NAFLD in a rat model.

Materials and methods: Following either splenectomy or sham operation, male Sprague-Dawley (SD) rats were fed a high-fat diet to drive the development of NAFLD; animals fed a normal diet were used as controls. Two months after surgery, livers and blood samples were collected. Serum lipids were measured; liver histology, phosphatase and tensin homologue deleted on chromosome 10 (PTEN) gene expression, and the ratio of pAkt/Akt were determined.

Results: Splenectomy increased serum lipids, except triglyceride (TG) and high-density lipoprotein (HDL), in animals fed either a high-fat or normal diet. Furthermore, splenectomy significantly accelerated hepatic steatosis. Western blot analysis and real-time polymerase chain reaction showed splenectomy induced significant downregulation of PTEN expression and a high ratio of pAkt/Akt in the livers.

Conclusions: The spleen appears to play a role in the development of NAFLD, via a mechanism involving downregulation of hepatic PTEN expression.

Figure 1

Splenectomy exacerbates steatosis in rats fed a high-fat diet. Hematoxylin and eosin staining (original magnification ×40) of livers from animals fed a normal diet + sham operation (a); a high-fat diet + sham operation (b); or a high-fat diet + splenectomy (c)

Figure 2

Splenectomy increases the concentration of serum lipids. Total lipids were extracted from the sera of animals and concentrations were determined. ND, normal diet; HF, high-fat diet; Sham, sham operation; SPX, splenectomy. ^#P < 0.05 compared with normal diet rats having undergone the same operation; *P < 0.05 compared with rats having undergone sham operation

Figure 3

Splenectomy increases the concentration of liver triglyceride (TG) in animals receiving a high-fat diet. Total liver TGs were extracted from the sera of animals and concentrations were determined. ^#P < 0.05 compared with normal diet rats having undergone the same operation; *P < 0.05 compared with rats having undergone sham operation

Figure 4

Splenectomy reduces PTEN expression, increasing Akt activity in rats fed a high-fat diet. (a) PTEN expression was determined at the protein level by western blot analysis (left and middle panel) and the mRNA level by RT-PCR (right panel). (b) Akt and pAkt levels were determined by western blot analysis. ND, normal diet; HF, high-fat diet; Sham, sham operation; SPX, splenectomy. *P < 0.05 compared with rats having undergone sham operation